Large-capacity dry-type transformers do not use oil immersion for cooling—the “oil tank, oil cooling” described in the original content belongs to oil-immersed transformers. Dry-type transformers rely on air or gas as the cooling medium, and their heat dissipation methods are strictly differentiated from oil-immersed types. Below is a detailed explanation of dry-type transformer heat dissipation principles, methods (classified by capacity), and core design logic.
Heat in dry-type transformers originates from internal losses, which must be dissipated in time to avoid insulation damage or safety hazards:
- Heat Source: Mainly from two types of losses—iron loss (hysteresis + eddy current loss in the core, constant during operation) and copper loss (I²R loss in windings, increases with load).
- Heat Dissipation Necessity: If heat accumulates, the winding temperature will exceed the insulation class limit (e.g., 180°C for Class H), leading to insulation aging, short circuits, or even fire (no explosion risk, as dry-type transformers have no flammable oil).
The choice of cooling method depends on the transformer’s capacity, as the ratio of external surface area to volume directly affects heat dissipation efficiency:
- For small-capacity transformers: Surface area/volume ratio is large, so natural cooling suffices.
- For large-capacity transformers: Surface area/volume ratio decreases (volume/loss increase with the cube of core size; surface area increases with the square), requiring enhanced cooling.
- Applicable Capacity: Generally ≤100kVA (e.g., SGB10-50kVA, SCB13-100kVA).
- Cooling Principle: Relies on two natural heat transfer mechanisms:
- Radiation: Heat is emitted from the transformer’s surface (core, windings, enclosure) to the surrounding air.
- Natural Convection: Hot air near the transformer rises, and cold air supplements it, forming a circulating airflow to take away heat.
- Key Features: No moving parts (fans), low noise (≤50dB), maintenance-free, and high reliability.
- Application Scenario: Indoor dry, clean environments (e.g., residential basement power distribution rooms, small office buildings) where fire safety is prioritized (replaces oil-immersed transformers to avoid oil fire risks).
- Applicable Capacity: ≥125kVA (e.g., SCB13-200kVA, SGB10-1600kVA).
- Cooling Principle: On the basis of natural convection, axial cooling fans (installed on the transformer’s top or side) are added to actively blow cold air through the winding gaps and core surfaces, accelerating heat dissipation.
- Key Design of CHH Power:
- Temperature Control: Equipped with a temperature controller that automatically starts fans when the winding temperature exceeds 100°C and stops them when it drops below 80°C—avoiding unnecessary energy consumption.
- Overload Support: With intact AF cooling and good external ventilation, the transformer can operate at 120% of rated load for a long time (e.g., a 200kVA transformer can carry 240kVA), meeting peak load demands.
- Key Features: High cooling efficiency (heat dissipation capacity increased by 30–50% compared to AN), compact size (avoids excessive volume from purely natural cooling), and adjustable cooling intensity.
- Application Scenario: Indoor industrial sites, commercial plazas, and data centers with large load fluctuations (e.g., shopping malls during holidays, factories during production peaks).
- Applicable Capacity: ≥2000kVA (e.g., SCB14-3150kVA for industrial plants).
- Cooling Principle: Combines air cooling with water cooling—internal fans blow air through a water-cooled heat exchanger (instead of directly onto windings), and circulating cooling water takes away heat from the exchanger.
- Key Features: Highest cooling efficiency, suitable for high-temperature, high-density installation environments (e.g., large-scale steel plants, chemical factories) where air cooling alone is insufficient.
To further improve heat dissipation efficiency and reliability, CHH Power integrates three key optimizations into dry-type transformers:
- Winding Structure: Uses segmented winding design with reserved air gaps (5–10mm) to facilitate airflow circulation and reduce heat accumulation.
- Material Selection: Adopts high-thermal-conductivity epoxy resin (thermal conductivity ≥0.3W/(m·K)) for casting windings, accelerating heat transfer from the conductor to the surface.
- Enclosure Design: For AF-cooled models, uses mesh-type enclosures (IP23) to ensure unobstructed air intake/exhaust—avoiding heat retention caused by closed enclosures.
The “oil tank, corrugated tank, radiator” mentioned in the original content are exclusive to oil-immersed transformers. Dry-type transformers have no oil-related components, so their cooling systems (air-based) must not be confused with oil-immersed types. This distinction is key to correct selection, installation, and maintenance.
